Aircraft frames are built for high strength to weight ratios, but vehicle frames normally target the stiffness to weight ratio.
If any part of your frame is getting close to the yield point of ordinary mild steel, then it is, almost by definition, flexing too much for geed handling. Lotus, among others, built many successful race cars, even at the Formula 1 level, from cheap ERW (electric resistance welded) tubing. Looking for a lighter and stiffer frame than the Norton 'Featherbed', Colin Seeley made his race frames from ERW, but with straight tubes. When asked why he didn't use stronger Reynolds tubing, he's reported to have said 'Nobody knows how to crash a motorcycle not quite hard enough to bend the frame'. Formula Ford cars at one time had a (cost control) rule that only ERW could be used in their construction (roll hoop excepted). It seems that at one time USA made ERW had a bad reputation for failing at the seam and was banned by some motorsport sanctioning bodies. Brazing Chrome Molly can lead to brittleness due to inter granular penetration if the metal gets too hot. That's why the Reynolds Manganese alloys are preferred for Brazing and Bronze welding. On Tue, 3 Dec 2019 at 19:59, Bill Dube via EV <[email protected]> wrote: > > Chrome-moly steel is about double the specific strength (ratio of > ultimate strength divided by density) of mild steel. That's why they > often use chrome-moly in airplanes, and never use mild steel. > > https://en.wikipedia.org/wiki/Specific_strength > > As you can see from the chart, mild steel has a specific strength of > 71-85 kN m/kg, while low-carbon steel has a specific strength of 46 kN m/kg. > Looking further down the chart, you can see why they use carbon fiber > composite (785 kN m/kg) to build modern airplanes. > > Chrome-moly (4130) is often chosen for its ease of fabrication and its > forgiving nature when abused. It can be welded (or brazed) without > subsequent heat treatment, and it deforms ~25% before failure. (It > stretches like taffy before it comes apart.) It also has a high fatigue > resistance. > > Bill D. > > About double On 12/4/2019 7:31 AM, Paul Compton via EV wrote: > > On Tue, 3 Dec 2019 at 03:27, Lawrence Rhodes via EV <[email protected]> > > wrote: > > > >> Using chromoly will reduce the weight. > > Oh, is Chrome Molybdenum Steel somehow magically lighter than mild Steel? > > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/index.html > INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) > -- Paul Compton www.morini-mania.co.uk www.paulcompton.co.uk (YouTube channel) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
